1. Field of the Invention
The present invention relates to an optical image stabilizer capable of reducing (correcting) image blur due to shaking of an optical apparatus such as a camera or an interchangeable lens.
2. Description of the Related Art
Such an optical image stabilizer corrects the image blur by moving (shifting) a correction lens constituting part of an image taking optical system or an image sensor photoelectrically converting an object image formed by the image taking optical system, with respect to a center axis (in other words, an optical axis of the image taking optical system). The correction lens and the image sensor are hereinafter collectively referred to as an “image stabilizing element”.
However, when nonuse of the optical image stabilizer is selected by a user or power supply of the optical apparatus is turned off, it is necessary to limit the movement (shift) of the image stabilizing element to keep it at a center of its movable range.
Therefore, many conventional optical image stabilizers include, as disclosed in Japanese Patent Laid-Open No. 2005-070113, a lock mechanism that mechanically keeps the image stabilizing element at the center of its movable range. The lock mechanism includes plural protrusions provided on an outer circumferential part of a shift member that holds the image stabilizing element and is movable integrally therewith, and a lock member that is rotatable about the center axis between a lock position to come into contact with the protrusions so as to limit the movement of the shift member and an unlock position to release the lock of the movement of the shift member.
The lock member is a ring-shaped member, and is rotatably supported by a supporting portion formed in a base member of the optical image stabilizer. Moreover, the lock member includes, at its inner circumferential part, lock portions coming into contact with the protrusions of the shift member so as to limit the movement of the shift member to bring the shift member into a locked state. Furthermore, the lock member is rotationally driven by a lock actuator such as a stepping motor.
However, as disclosed in Japanese Patent Laid-Open No. 2005-070113, the conventional optical image stabilizers generally employ a configuration in which the supporting portion of the base member rotatably supports an outer circumferential part of the lock member, and the lock member rotates while its outer circumferential part slides with respect to the supporting portion. Such a configuration easily increases friction between the rotating lock member and the supporting portion, which causes problems that the size of the lock actuator may be increased and smooth rotation of the lock member may be prevented.